Re: [PATCH] Fix: membarrier: add missing preempt off around smp_call_function_many

[Mathieu Desnoyers]

Hi Linus, Peter, Ingo,

Now that membarrier.c has been moved from kernel/ to kernel/sched/, should
I route this membarrier fix through the scheduler maintainers, or is it OK
to send it to you directly ?

Thanks,

Mathieu

----- On Dec 15, 2017, at 2:23 PM, Mathieu Desnoyers mathieu.desnoyers@xxxxxxxxxxxx wrote:

> smp_call_function_many requires disabling preemption around the call.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> CC: Boqun Feng <boqun.feng@xxxxxxxxx>
> CC: Andrew Hunter <ahh@xxxxxxxxxx>
> CC: Maged Michael <maged.michael@xxxxxxxxx>
> CC: Avi Kivity <avi@xxxxxxxxxxxx>
> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> CC: Paul Mackerras <paulus@xxxxxxxxx>
> CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> CC: Dave Watson <davejwatson@xxxxxx>
> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: "H. Peter Anvin" <hpa@xxxxxxxxx>
> CC: Andrea Parri <parri.andrea@xxxxxxxxx>
> CC: <stable@xxxxxxxxxxxxxxx>	# v4.14
> ---
> kernel/sched/membarrier.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
> index dd7908743dab..9bcbacba82a8 100644
> --- a/kernel/sched/membarrier.c
> +++ b/kernel/sched/membarrier.c
> @@ -89,7 +89,9 @@ static int membarrier_private_expedited(void)
> 		rcu_read_unlock();
> 	}
> 	if (!fallback) {
> +		preempt_disable();
> 		smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
> +		preempt_enable();
> 		free_cpumask_var(tmpmask);
> 	}
> 	cpus_read_unlock();
> --
> 2.11.0

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com